You might have heard that BMI increases the odds of shoulder dystocia. But by how much?
Let's look at the evidence and address the common misconception that the risk is high when you're plus size.
Please note this article is not a substitute for professional medical advice. Address any questions or concerns with your care provider.
Also, BMI is commonly used in studies to categorize people by their weight relative to their height. We use BMI in this article to share information about shoulder dystocia risks, but we acknowledge that BMI is problematic and doesn't give a complete view of someone's health.
What is shoulder dystocia?
During vaginal birth, shoulder dystocia happens when one or both of a baby's shoulders get stuck behind the pubic bone. It is a rare but urgent medical emergency.
The good news? Most of the time, shoulder dystocia is managed safely and without complications, thanks to the fast responses and special techniques that your healthcare team is trained in.
Occasionally, the baby might have minor injuries, like a temporary arm weakness or, very rarely, a broken collarbone. For the birthing individual, there might be some tearing or bleeding. But keep in mind these complications aren't typical.
What is associated with the highest risk for shoulder dystocia?
A study from 2023 examined shoulder dystocia in about 10 million vaginal births in the U.S. from 2016 to 2019 (Youssefzadeh et al., 2023).
This data came from the National Inpatient Sample, which randomly gathers information from 20% of inpatient records in participating centers in the United States.
The study was designed to accurately represent the United States population by including individuals with different health conditions.
In the study, women aged 15 – 54 had various health conditions like diabetes (either before pregnancy or developed during), high blood pressure disorders, and more. Some had complications during labor, like needing assistance with tools like a vacuum or forceps.
Out of all the births studied, shoulder dystocia happened in 228,120 cases. That's 23 out of every 1,000 births or 2.3%.
The study found that having a big baby, having diabetes before or during pregnancy, and using a vacuum during birth were the main factors linked to shoulder dystocia.
Other factors that were somewhat linked to increased risk of shoulder dystocia:
- Older or younger age
- Black individuals (from systemic effects of racism)
- Chronic health conditions
- BMI > 30
- Term premature rupture of membranes
- High weight gain during pregnancy
- Giving birth after 40 weeks of pregnancy
- Labor induction or augmentation
What is my increased risk of shoulder dystocia with a BMI above 30?
When we look at the numbers in the study, people with a BMI of 30 or higher had a 3.4% chance (or 34 out of 1000) of experiencing shoulder dystocia.
In comparison, those with a BMI below 30 had a 2.2% chance (or 22 out of 1000).
As highlighted in our article on discussing increased pregnancy risks, let's view this from another angle.
Rather than dwelling on the 3.4% risk, let's take a fresh perspective based on the data.
With a BMI over 30, there's a 96.6% likelihood you won't incur shoulder dystocia during childbirth – and those odds sound really good!
Being plus size, you might encounter biases where people make unfair assumptions about your health and your chances of having a healthy pregnancy.
Such myths sometimes arise from concerns about shoulder dystocia or soft tissue dystocia. For instance, hearing that someone's vagina is too fat to give birth is scientifically incorrect and deeply hurtful.
Instead of letting misconceptions or negative comments weigh you down, keep the lines of communication open with your care provider. They can offer guidance and facts tailored just for you.
Remember, as with the shoulder dystocia statistics, the overall increased risks are generally low during a plus size pregnancy.
By focusing on your wellness during pregnancy and connecting with a size-friendly care provider, you're setting the stage for a more relaxed, positive experience with fewer worries.
Special thanks to Anna Bertone for her assistance with the research for this article.
- Davis DD, Roshan A, Canela CD, et al. Shoulder Dystocia. [Updated 2022 Sep 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan / ncbi.nlm.nih.gov/books/NBK470427/
- Youssefzadeh AC, Tavakoli A, Panchal VR, Mandelbaum RS, Ouzounian JG, Matsuo K. Incidence trends of shoulder dystocia and associated risk factors: A nationwide analysis in the United States. Int J Gynaecol Obstet. 2023 Aug;162(2):578-589. doi: 10.1002/ijgo.14699. Epub 2023 Mar 1. PMID: 36707062.
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- Nonstress Tests for High BMI in Pregnancy: Vital or Excessive? - July 30, 2023
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